Cyanoacrylate adhesive compositions for bonding glass

ABSTRACT

A one-part adhesive composition for bonding glass including: 
     (a) a cyanoacrylate monomer; 
     (b) 15 to 60% w/w of at least one plasticizer by weight of the composition; 
     (c) 0.01% to 5.0% w/w of at least one silane by weight of the composition. The silane may be is selected from the silanes of the Formula: 
     
       
         R′ (4−n)  Si(OR″) n   
       
     
     wherein: n=1 to 4; and 
     each R′ and R″ which may be the same or different represents H, hydrocarbyl, aryl, hydrocarbylaryl or a substituted derivative thereof, or those of the formula:                    
     wherein R 1 , R 2 , R 3 , and R 4 , each independently represent hydrocarbyl, aryl, hydrocarbylaryl, or a substituted derivative thereof, H or halogen or the group —OR 5  wherein R 5  represents hydrocarbyl, aryl or hydrocarbylaryl or a substituted derivative thereof and any two of the groups R 1 , R 2 , R 3  and R 4  may be taken together with the silicon atom to form a cycle; 
     with the proviso that at least one of R 1 , R 2 , R 3  or R 4  represents hydrocarbyl, aryl, hydrocarbylaryl or a substituted derivative thereof.

TECHNICAL FIELD

This invention relates to cyanoacrylate adhesive compositionsparticularly intended for bonding glass.

BACKGROUND ART

It is known that “instant” adhesives based on cyanoacrylate esters,while they are effective bonding agents for a wide variety of materials,do not give a permanent bond in joints involving glass. A strong bond toglass is obtained initially but generally the joint fails after a periodof weeks or months at room temperature (RT) conditions. This majordeficiency of cyanoacrylate adhesives is not fully understood. Whilethis invention is not limited by-any theory, the deficiency is likely tobe related to the extremely rapid speed at which these adhesives cure onglass aided by the basic nature of the surface. High stresses aregenerated in the bond line immediately adjacent to the glass, at amolecular level. These stresses make the polymer in the bond lineuniquely susceptible to chemical or physical degradation, for example asa response to contraction and expansion of the joint with changes in RTor to hydrolytic attack by atmospheric moisture.

This major limitation of cyanoacrylate adhesives has persisted for overfour decades since the materials were originally invented. Commerciallyavailable cyanoacrylate products are generally precluded from use inbonding glass particularly glass to glass bonds.

Kol'tsova et al, abstract of.Russian patent SU 1564172 describes amethod of bonding cut glass by treating the surface to be joined with20% of a 1:1 PhMe—Me₂CO solution of a Si-epoxy-containing oligomer,drying and then applying the adhesive (alpha-cyanoacrylate), andsubsequently contacting the surfaces. The method described uses atwo-part system.

JP 06100838 describes adhesives containing alpha-cyanoacrylates and anorganosilicon compounds specifically Ph₂SiH₂.

GB 1,529,105 discloses cyanoacrylate based adhesives for glass and steelcontaining alpha-cyanoacrylates, 20% to 60% by weight of the compositionof a plasticizer which is miscible with the ester and from 0.015% to0.15% by weight of the composition of a carboxylic acid which is solublein the ester. The adhesive is designed so as to be easily debonded whendesired.

JP 52076344-A describes the pretreatment of substrates by application oforgano-silane compounds of the formula R—Si(X)₃ where R is alkyl,alkenyl, allyl, aralkyl, cycloalkyl or cycloalkenyl group with 1 to 18carbon atoms inclusive of those substituted by halogen, ether, OH,ester, epoxy and other groups. X is OCH₃, OC₂H₅, OC₃H₇, OC₄H₅, OH, Cl,Br, I, O—C(O)—CH₃. The pretreatment process is said to eliminate thedisadvantages of alpha-cyanoacrylate based adhesives observed whenapplied on glass, iron and ceramics, of deterioration on weathering,water resistance and impact resistance.

GB 1,430,506 describes an adhesive composition containingN,N′-substituted bis-maleimide, alpha-cyanoacrylate and optionallycontaining a silane coupling agent or a diamine. The adhesive can beused to bond metal, glass, ceramic and heat resistant films and toproduce resin laminations and flexible dielectric films.

GB 1 373 559 describes the use of an alkoxy or acyloxy silane in or witha cyanoacrylate adhesive composition for glass-glass or glass-rubberbonding. However the majority of the examples describe the use of thesilane as a primer. Although a one-part composition is also described,there is no suggestion of including a plasticizer in it.

SU 1,328,361-A discloses a two-part cyanoacrylate adhesive system usingsilane derivatives which may be used in glass-glass bonding.

EPO 151,527 discloses cyanoacrylate adhesive compositions which employcalixarene compounds as additives and which give substantially reducedfixture and cure times on wood and other deactivating surfaces such asleather, ceramic, plastics and metals with chromate treated or ceramicoxide surfaces. Fumed silica fillers treated with polydialkylsiloxanesor trialkylsilanes may be employed as fillers. Plasticizers areoptionally included. No mention is made of glass bonding.

U.S. Pat. No. 4,906,317 describes cyanoacrylate compositions whichemploy silacrown compounds as additives to give substantially reducedfixture and cure times on wood and other deactivating surfaces such asleather, ceramic, plastics and metals with chromate treated or acidicoxide surfaces. No mention is made of glass bonding.

The silacrowns of U.S. Pat. No. 4,906,317 are not silanes within themeaning of the term silane as used herein. As stated the silacrowns areprepared by transesterification of alkoxysilanes with polyethyleneglycols i.e. they are reaction products of silanes but are notthemselves silanes. Furthermore they do not act as free silanes.Silacrowns function as accelerators in the composition of U.S. Pat. No.4,906,317. The silanes of the present invention act as coupling agents,a function which a silacrown does not perform.

The specific silacrowns disclosed in U.S. Pat. No. 4,906,317 and whichare represented by the following formula do not function as silanes:

wherein R² and R³ are organo groups which do not themselves causepolymerisation of the cyanoacrylate monomer, R⁴ is H or CH₃ and n is aninteger. Examples of suitable R² and R³ groups are straight chain orbranched chain alkyl groups having 1 to 12 carbon atoms (which may besubstituted with a substituent such as a halogen atom or an alkoxygroup) a straight chain or branched chain alkenyl group having 2 to 12carbon atoms, a straight chain or branched chain alkynyl group having 2to 12 carbon atoms, a cycloalkyl group, an aralkyl group or an arylgroup, alkoxy groups such as methoxy, and aryloxy groups such asphenoxy. The R² and R³ groups may contain halogen or other substituents,an example being trifluoropropyl. Groups not suitable as R² and R³groups are basic groups such as amino, substituted amino and alkylamino.

U.S. Pat. No. 4,906,317 discloses the optional inclusion of fumedsilicas treated with polydialkylsiloxanes or trialkoxyalkylsilanes. Thefumed silicas are used as thickeners. The purpose of the silane which isretained on the surface of the silica is to maintain the fumed silica ina dispersion within the composition.

Fumed silicas are referred to in EP-A-0 209 067 also. Again the fumedsilica is treated with trialkoxyalkysilane.

The present Applicants understand that trialkoxytrialkyl silane presentin the compositions of U.S. Pat. No. 4,906,317, EP-A-0 209 067 andEP-A-0151 527 is chemically bound and immobilized on the surface of thesilica in accordance with the function to retain the silica in adispersed phase. It is not a “free” silane in that it is not a mobilecomponent of the composition. It does not function independently of thesilica in the composition. In addition, it is not free to act as aconventional coupling agent and in particular does not act as a silanecoupling agent or adhesion promoter. A coupling agent or adhesionpromoter acts at the interface of the adhesive and the substrate beingbonded to provide a better bond between the adhesive and the substrate.

While the EP '067 patent also mentions the optional inclusion ofplasticisers the object is to provide stable cyanoacrylate compositionswith good thixotropic properties. It is not directed to the problem ofglass bonding.

EP-A-0 137 849 relates to an alpha-cyanoacrylate-based instant adhesivecomposition containing benzophenonetetracarboxylic acid or itsanhydride, and optionally plasticisers. A heat resistant composition issought. No reference to the problem solved by the present invention,namely cyanoacrylate glass bonding is made in this document.

While the constituents mentioned herein are well known individually aspolymer modifiers or adhesion promoters, their particular combinationand use in this invention are unique, and the benefits gained ineffectively bonding glass are unexpected. For example the compositionsdisclosed in GB 1,529,105 contain high levels of phthalate plasticizerin ethyl cyanoacrylate but the resulting adhesives are claimed to besuitable only for temporary bonding purposes on glass or steel. Two-partadhesive systems where silanes are employed to pretreat glass aredescribed in Japanese Patent JP 5207634. The inconvenience of a two-partsystem is overcome by the one-part adhesive composition of the presentinvention.

It would be desirable to provide cyanoacrylate based adhesivecompositions that overcome the deficiencies and limitations describedabove and gives strong durable adhesive bonds on glass, includingcrystal glass. It would also be desirable to provide one-partglass-bonding adhesive compositions, which are stable on storage and arealso effective adhesives for bonding a wide range of other materials.

SUMMARY OF THE INVENTION

The present invention meets those desires by providing a one-partadhesive composition including (a) a cyanoacrylate monomer; (b) at leastone plasticizer in the amount of 15 to 60% w/w by weight of thecomposition; and (c) at least one silane in the amount of 0.01% to 5.0%w/w by weight of the composition.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view with plane polarized light (sodium d line) of glassbonded with a layer 1 or standard n-butyl cyanoacrylate adhesive(adhesive A in Example 1). Polarized light is used to highlight thestress patterns 2 induced in the glass.

FIG. 2 is a view similar to FIG. 1 of glass bonded with a layer 1 ofplasticized n-butyl cyanoacrylate adhesive (adhesive B in Example 1).The polarized light photograph shows the absence of stress patterns whenthe glass is bonded with n-butyl cyanoacrylate containing 30% dibutylphthalate (DBP).

FIG. 3 shows the effect of various levels of DBP on n-butyl CA bondstrength (glass bonds) and durability under repetitive dishwashercycles. The values plotted are taken from Table I of Example 2.

DETAILED DESCRIPTION OF THE INVENTION

As noted above the present invention meets those desires by providing aone-part adhesive composition including (a) a cyanoacrylate monomer; (b)at least one plasticizer in the amount of 15 to 60% w/w by weight of thecomposition; and (c) at least one silane in the amount of 0.01% to 5.0%w/w by weight of the composition.

A desirable content range for the plasticizer is 15 to 45% w/w of theadhesive composition, with a more desirable range being 20 to 40% w/w,such as 25 to 35% w/w. A suitable content range for the silane is 0.02to 3.0% w/w of the adhesive composition, With a more desirable rangebeing of 0.05 to 1.0% w/w.

The cyanoacrylate monomer suitably is of the formula CH₂=C(CN)COORwherein R is selected from:

alkyl having at least 2 carbon atoms, more particularly having 2-10carbon atoms, including: ethyl; n-propyl; iso-propyl; n-butyl;iso-butyl; sec-butyl; n-pentyl.; iso-pentyl; n-hexyl; iso-hexyl;n-heptyl; 2-ethylhexyl; n-octyl; n-nonyl; n-decyl; alkoxyalkyl having atleast 2 carbon atoms in the alkyl group, more particularly having 2-10carbon atoms in the alkyl group, and especially having 1-10 carbon atomsin the alkoxy group, including; 2-methoxyethyl; 2-ethoxyethyl;3-methoxybutyl; 1-methoxy-2-propyl; allyl, propargyl, cyclohexyl, andphenyl.

R is desirably butyl or octyl.

The cyanoacrylate ester for use in the present invention is suitablyn-butyl-2-cyanoacrylate, although other cyanoacrylate esters may also beused.

The term “silane” as used herein includes silane hydrides andsubstituted silanes.

Suitable silanes may be of the formula R′_((4−n)) Si(OR″)_(n) whereinn=1 to 4; each R′ and R″, which may be the same or different, representsH, hydrocarbyl, aryl, hydrocarbylaryl or a substituted derivativethereof.

Desirably, n is 2 or 3.

Desirably, R″ is C₁-C₅ alkyl, C₁-C₅ alkenyl, or —COR″′ in where R″′ isC₁-C₅ alkyl or C₁-C₅ alkenyl, or a substituted derivative thereof.

Desirably R′ is C₁-C₅ alkyl, C₁-C₅ alkenyl,

where m is 0 to 5

or —(CH₂)_(m)—O—CO—R″′ in where R″′ and m are as defined above, or asubstituted derivative thereof.

The silane may contain a cyclic structure. If the Si atom forms part ofa cycle it should not form part of a silacrown cycle (crown structure).If the Si atom forms part of a cycle, the cycle desirably shouldcomprise no more than three oxygen atoms.

Other silanes include those of the general formula:

wherein R₁, R₂, R₃, and R₄, each independently represent hydrocarbyl,aryl, hydrocarbylaryl, or a substituted derivative thereof, H or halogenor the group —OR₅ wherein R₅ represents hydrocarbyl, aryl orhydrocarbylaryl or a substituted derivative thereof and any two of thegroups R₁, R₂, R₃ and R₄ may be taken together with the silicon atom toform a cycle;

with the proviso that at least one of R₁, R₂, R₃ or R₄ representshydrocarbyl, aryl, hydrocarbylaryl or a substituted derivative thereof.

The cyclic group may be unsubstituted or substituted with halogen or maybe bridged or interrupted by one or more oxo groups and suitably four toeight atoms form the cycle.

Examples of cyclic silanes of this general formula include:

cyclohexyldimethylchlorosilane,

cyclohexyldimethylsilane, (cyclohexylmethyl)trichlorosilane.

cyclohexyltrichlorosilane,.

(3-cyclopentadienylpropyl)-triethoxysilane,

cyclopentamethylenedichlorosilane,

cyclopentamethylenedimethylsilane,

cyclotetramethylenedichlorosilane,

cyclotetramethylenedimethylsilane,

cyclotrimethylethylenedichlorosilane,

cyclotrimethylenedimethylsilane,

dihexyldichlorosilane,

diisopropenoxydimethylsilane,

diisopropylchlorosilane,

dimesityldichlorosilane,

1,1-dimethyl-1-sila-2-oxacyclohexane,

Si-methyl(4-chloro-3,5 dimethyl)benzooxasilepin methyl ester, andbenzooxasilepindimethylester.

The term “hydrocarbyl” as used herein means straight-chain, branched orcyclic, aliphatic hydrocarbyl including alkyl, alkenyl and alkynyl.Hydrocarbyl groups should contain from 1 to 10 carbon atoms, such asfrom 1 to 5 carbon atoms, and aryl and hydrocarbylaryl groups shouldcontain from 6 to 20 carbon atoms, such as from 6 to 10 carbon atoms.Hydrocarbyl groups are desirable, especially alkyl or alkenyl groups.The term aryl includes fused ring systems. The term hydrocarbylarylincludes a cyclic hydrocarbyl fused to an aryl ring.

A substituted derivative may also suitably be substituted with one ormore halogens groups or substituted or interrupted or bridged by one ormore oxo groups. Halogen may be chlorine, bromine, fluorine or iodine.

The silane constituent can suitably be one or more of a range of alkoxysilanes such as vinyltriethoxy silane, vinyltrimethoxy silane,glycidoxypropyltrimethoxy silane, ethyltriethoxy silane,dimethyldiacetoxy silane, propyltriacetoxy silane andvinylmethyldiacetoxy silane. Silanes giving a particularly good balanceof compatibility and performance include methyltriacetoxy silane,3-(methacryloxy)propyltrimethoxy silane and vinyltriacetoxy silane.

The invention also relates to a method of bonding substrates using acomposition as described above. In that method, the composition isapplied to at least one of the substrates and thereafter the substratesare brought together. In particular the adhesive composition of theinvention is suitable for bonding glass substrates giving a more durablebond than with other compositions.

The plasticizer component can be selected from one or more conventionalmaterials used for this purpose in adhesive compositions provided thatthe plasticizer is compatible and soluble in cyanoacrylate esters (seeGB 1 529 105). Examples include alkyl phthalates, azelates, adipates,sebacates, citrates, phosphates, succinates, benzoates andtrimellitates. Desirable plasticizers are dibutyl phthalate, benzylbutylphthalate, diheptyl phthalate, dibutyl sebacate and diethyleneglycoldibenzoate. Blends of two or more different plasticizers are alsobeneficial.

It will be understood that the adhesive composition may contain ananionic polymerization inhibitor and/or free radical polymerizationinhibitor in conventional amounts [see U.S. Pat. No. 4,460,759(Robins)]. The cyanoacrylate adhesive compositions may also containsequestering agents e.g. calixarenes, anhydrides, stabilizers,thickeners, silicas, adhesion promoters, dyes, heat resistant modifiers,perfumes and such like.

Suitably the composition of the invention comprises fillers other thansilica.

The adhesives of this invention have commercial shelf-life stability.

The present invention will be further described with reference to thefollowing examples and comparative examples. It should be noted that thescope of the invention is not limited by these examples.

EXAMPLES

Examples 1, 2 and 3 illustrate properties of constituents of theadhesive compositions of the invention but do not relate to the adhesivecompositions of the invention per se.

Abbreviations Used in This Section:

CA=cyanoacrylate

RT=Room temperature

RH=Relative humidity

DBP=dibutyl phthalate

Example 1

Adhesives Were Prepared as Follows:

A. 11-Butyl cyanoacrylate.

B. n-Butyl cyanoacrylate containing 30% dibutyl phthalate plasticizer.

C. Ethyl cyanoacrylate.

D. Ethyl cyanoacrylate containing 30% dibutyl phthalate plasticizer.

E. Methyl cyanoacrylate.

F. Methyl cyanoacrylate 30% dibutyl phthalate plasticizer.

G. Allyl cyanoacrylate.

H. Allyl cyanoacrylate containing 30% dibutyl phthalate plasticizer.

I. 2-methoxy ethyl cyanoacrylate.

J. 2-methoxy ethyl cyanoacrylate containing 30% dibutyl phthalateplasticizer.

Test pieces of soda glass with dimensions of 38.1×38.1×6.35 mm werebonded with above adhesives. The bond involved the overlap of thecomplete surface area of 1451.6 mm². The bonds were allowed to cure for24 hours at RT and then examined for the presence of stresses in theglass by viewing with plane polarized light (Sodium d line). Resultswere as follows:

Stressed or partially stressed (see FIG. 1) Adhesives A, C, D, E, F, G,H, I, J. Absence of stress patterns (see FIG. 2) Adhesive B

This example shows that plasticized n-butyl cyanoacrylate generates astress-free bond on glass while other cyanoacrylate/plasticizercombinations generate a stressed or partially stressed joint. While itis desired to have a completely stress free joint it will be appreciatedthat bonds with reduced bond stress are acceptable for the purposes ofthe invention.

Example 2

n-Butyl cyanoacrylate monomer was prepared by the Knoevengalcondensation reaction between n-butyl cyanoacetate and formaldehyde andpurified by distillation. The monomer was stabilized against spontaneouspolymerization by addition of 30 ppm sulphonic acid and 1000 ppmhydroquinone. Adhesive formulations containing the stabilized n-butylcyanoacrylate monomer and various proportions of di-n-butylphthalateplasticizer were prepared on a weight/weight basis by direct mixing ofthe two liquids. For example a 10% solution of di-n-butyl phthalateplasticizer in n-butyl cyanoacrylate monomer was prepared by addition oflog of the plasticizer to 90 g of monomer.

Adhesive formulations containing zero %, 10%, 20%, 25%, 30%, 40%, 50%,60% and 70% di-n-butyl phthalate were prepared in this manner.

The adhesive formulations were used to bond soda glass test pieces ofdimensions 50.8×25.4×4 mm which were precleaned with isopropyl alcoholand deionized water and allowed to dry. A number of overlapped jointswith a bonded area of 322.5 mm² were prepared with each adhesiveformulation and allowed to cure for 24 hours at RT (20° C.+3° C.). Thebond strengths were determined using an Instron Model 1185 tensiletesting machine using a crosshead pulling speed of 2 mm/min. The bondswere tested for durability by subjecting them to a sequence of washingcycles in a domestic dishwasher (Tricity Bendix Model HEL8). The bondswere examined for integrity after each cycle and the number of cycles tobring about the bond failure was recorded. The test results for bonddurability (No. of dishwasher cycles) and bond strength are summarizedin Table I. The results suggest that (a) bond strength decreases withincreasing proportions of plasticizer and levels greater than about 40%result in bonds of reduced strengths and (b) the concentration ofplasticizer needed for good durability is about 30%-50%.

TABLE I (Example 2) Bond Strength and Durability of glass-glass bondedwith n-butyl cyanoacrylate adhesives containing various levels ofplasticizer. Bond Strength Durability (No. of Dibutylphthalate (%)(N/mm²) Dishwasher Cycles)  0 2.7 5 10 3.2 3 20 3.2 5 25 1.94 5 30 2.4650 40 1.86 90 50 0.80 90 60 0.32 20 70 0.08 10

The above table (Table I) is used in the present example to illustratethe trend in bond strength and durability of the bond with increasingconcentration of dibutylphthalate. The result shown for 30%dibutylphthalate (as compared to that for 25% and 40% dibutylphthalate)would appear to be due to experimental variations, as can be seen withreference to Table II of Example 3. This experimental variation does notoccur with the compositions of the invention.

Example 3

A selection of plasticizing materials were added-to a-butylcyanoacrylate at a concentration of 30% w/w. In practice this entailedthe addition of 30 g of plasticizer to 70 g of butyl cyanoacrylatemonomer with mixing to give a homogeneous solution. These solutions werein effect plasticized adhesives and each was used to bond glass testpieces in the manner described in Example 2.

The bonded test pieces were clamped and allowed to cure for 24 hours atRT. The clamps were removed and a measure of the durability of the bondsdetermined by subjecting them to repeated washing cycles in a domesticdishwasher as described in Example 2. The bonds were examined after eachcycle and the number of cycles needed to induce failure of the bond wasrecorded.

A list of the plasticizing materials used in the example is given inTable II together with the dishwasher durability results. The resultsshow several of the plasticizing materials, e.g. dibutyl phthalate anddiethyleneglycol dibenzoate, giving enhanced durability relative to theunplasticized control.

TABLE II (Example 3) ADHESIVE All based on 30% w/w DISHWASHER TESTPlasticizer in butyl (No. of Cycles to bond failure) cyanoacrylate BONDA BOND B BOND C Dibutyl Phthalate 6 6 11  Benzylbutyl Phthalate 6 8 8Diisoheptyl Phthalate 4 6 6 Diheptyl Phthalate 6 6 6 Diocytyl Phthalate4 4 4 Diisooctyl Phthalate 4 6 6 Dinonyl Phthalate 4 4 4 DiisononylPhthalate 4 4 4 Diisodecyl Phthalate 4 4 4 Diisooctyl Azelate 4 4 4Dioctyl Azelate 4 4 4 Diisopropyl Adipate 4 4 4 Diisobutyl Adipate 4 4 4Di-2-ethylhexyl Adipate 4 4 4 Diisodecyl Adipate 4 4 4 Dibutyl Sebacate6 6 6 Diethyl Sebacate 6 6 6 Dioctyl Sebacate 4 4 4 Tributyl-o-acetylCitrate 4 4 4 n-Butyl Citrate 4 6 6 Tritolyl Phosphate 4 6 6 Tris(2-ethylhexyl) Phosphate 4 4 4 n-Butyl Oleate 4 4 4 DiethyleneglycolDibenzoate 6 6 8 Diethylhexyl Succinate 4 4 4 Bayer Silicone Oil 4 4 4Trihexyl Trimellitate 4 4 4 Dioctyl Teraphthalate 4 4 4 Control (butylcyanoacrylate alone) 4 4 4

Example 4

Adhesive formulations based on butyl cyanoacrylate monomer (as describedin Example 2) were prepared containing 30% w/w dibutyl phthalate (DBP)as constant and 0.2% of a selection of silanes as outlined in thefollowing table of test results. The silanes were initially dissolved inthe DBP before adding to the monomer (see Example 2 for details).

The adhesive formulations were used to bond soda glass test pieces ofdimensions 50.8×25.4×4 mm which were precleaned with isopropyl alcoholand deionized water and allowed to dry. A number of overlapped jointswith a bonded area of 322.5 mm² were prepared with each adhesiveformulation. The joints were clamped and allowed to cure for 24 hours atRT (20° C.+3° C.) before any further testing. The bonds were tested fordurability by subjecting them to a sequence of washing cycles in adomestic dishwasher (Tricity Bendix Model HEL8). The bonds were examinedfor integrity after each cycle using light hand pressure and the numberof cycles to bring about bond failure was recorded. The test results forbond durability (No. of dishwasher cycles) are recorded below for eachsilane-containing formulation and the findings show clear evidence ofhigh resistance of the bonded glass test pieces to the specifiedtreatment. The controls without silane showed poor resistance as did aformulation containing silicon tetraacetate.

Dishwasher Test (Number of Cycles to bond failure) Silane Type (all at0.2%) Run 1 Run 2 Run 3 Vinyltriethoxy silane 282 292 302Vinyltrimethoxy silane 172 172 282 Glicidoxypropyltrimethoxy silane 292302   282+ Vinyltriacetoxy silane 162 202 262 Ethyltriethoxy silane 152172 192 Dimethyldiacetoxy silane 125 172 252 Propyltriacetoxy silane 117142 152 Vinylmethyldiacetoxy silane 142 172 252 Silicon Tetraacetate 7 7 7 None (control) 5 7  8

Example 5

Glass bonding adhesive formulations were prepared as follows and used tobond glass test pieces which were then tested for resistance to failurewhen aged in (a) high humidity conditions and (b) immersed in water.

Formulation A: n-butyl cyanoacrylate monomer containing 20%dibutylphthalate (DBP) and 0.06%

3-(methacryloxy)propyltrimethoxysilane, prepared as described in Example2 above.

Formulation B: As formulation A above but containing 20% DBP and 0.3%methyltriacetoxysilane.

Formulation C: As formulation A above but containing 20% DBP and 30 0.3%methyltrimethoxysilane.

Formulation D: n-butyl cyanoacrylate monomer containing 20% DBP.

The adhesive formulations were used to bond soda glass test pieces ofdimensions 50.8×25.4×4 mm which were precleaned with isopropyl alcoholand deionized water and allowed to dry. A number of overlapped jointswith a bonded area of 322.5 mm² were prepared with each adhesiveformulation. The joints were clamped and allowed to cure for. 24 hoursat RT (20° C.+3° C.). The resistance to humidity was determined byageing the bonded test pieces in a cabinet maintained at 40° C./95%Relative Humidity (RH) and inspecting daily until bond failure occurred,the integrity of the joint being confirmed by light hand pressure.Resistance to water was determined by immersing the bonded test piecesin water which was stored at RT (20° C.+3° C.) until bond failure (astested daily by light hand pressure). The attached results showexcellent durability under above severe ageing conditions except withFormulation D which had no added silane.

Humidity Ageing at 40° C./95% RH Water Immersion Ageing (days to bondfailure) (days to bond failure) FORMULATION Test 1 Test 2 Test 1 Test 2Formulation A   300+   300+   315+   315+ Formulation B   300+   300+281 315 Formulation C   300+   300+   300+ 138 Formulation D  4  4  8  8

Example 6

The viscosities mentioned in this Example were measured by theCannon-Fenske Routine Viscometer method according to ASTM D445 (AmericanSociety for Testing and Materials). A size 200 or 300 Cannon-FenskeRoutine Viscometer was used and all determinations were carried out in awater bath at 25° C.

Glass bonding adhesive formulations containing thickeners were preparedas follows:

Premix A. 25 g of polymethylmethacrylate (PMMA) powder were added to 475g of n-butyl cyanoacrylate monomer with continuous mixing. When thepowder was fully dispersed the mixture was heated for 15 minutes at 70°C. to give a clear solution which was allowed to cool to RT.

Formulation A. 70 g of Premix A above were blended with 30 g ofdibutylphthalate (DBP) to give an adhesive formulation containing 30%dibutylphthalate and 3.5% PMMA. The viscosity was 31 mPas.

Formulation B. 0.2 g of methyltriacetoxysilane were dissolved in 30 g ofdibutylphthalate (DBP). This solution was then added to 70 g of Premix Aabove to give a final adhesive formulation containing 30% DBP, 3.5% PMMAand 0.2% methyltriacetoxysilane.

Formulation C. 70 g of Premix A above were blended with 30 g ofbenzylbutylphthalate to give an adhesive formulation containing 30%benzylbutylphthalate and 3.5% PMMA. The viscosity was approximately 31mPas.

Formulation D. 0.2 g of methyl triacetoxysilane were dissolved in 30 gof benzylbutylphthalate (BBP). This solution was then added to 70 g ofPremix A above to give a final adhesive formulation containing 30% BBP,3.5% PMMA and 0.2% methyltriacetoxysilane.

Soda glass test pieces of dimensions 50.8×25.4×4 mm were cleaned withisopropyl alcohol followed by deionized water and allowed to dry.Overlapped joints with a bonded area of 322.5 mm² were prepared witheach adhesive of Formulations A, B, C and D above and allowed to curefor 24 hours at RT (20° C.+3° C.). The bonds were then subjected torepeated cleaning cycles in a domestic dishwasher as described earlierand the time to bond failure noted. The results demonstrate that theadhesive formulations have excellent durability.

Bond Durability (Dishwasher Cycles) Adhesive Formulation Run 1 Run 2 Run3 A (DBT + PMMA) 162 172 192 B (DBT + PMMA + Silane) 262 332 332 C(BBP + PMMA) 562 572 612 D (BBP + PMMA + Silane) 432 502 512

In these tests, formulation C which did not contain silane showedsomewhat better bond durability than formulation D which containedsilane but this result is not of particular relevance because bothformulations showed bond durability well beyond the number of cycles tobe expected in a normal lifetime of a bonded article. The presentinventors have found that there is consistency to the bond durabilityexhibited if a silane is present. The composition of the presentinvention gives consistently good bond durability. Formulation Bcontaining silane out performed Formulation A which did not containsilane. Benzylbutyl phthalate (BBP) is a less desirable plasticizerbecause of its toxicity which would make it less suitable for use in acommercial adhesive.

Example 7

An n-butyl cyanoacrylate adhesive containing 30% w/w dibutylphthalateplasticizer and 0.2% methyltriacetoxysilane was prepared as in Example 8below and used for bonding crystal glass as described below.

Various household ornaments manufactured from lead crystal glass(minimum 24% Pb0) were broken to give irregular shaped fragments. Thefragments were bonded along the line of fracture and the parts heldtogether until the adhesive had fixtured to give handling strength. Thejoints were allowed to cure fully for 24 hours at RT. The bonds werethen tested for durability by repeated cycles in a domestic dishwasheras described in Example 2 above. The attached test results showexcellent resistance to this demanding treatment.

Type of lead crystal Fixture Time Dishwasher (Cycles) glass (Seconds)Run 1 Run 2 Waterford Crystal 15-30 35 67 Galway Crystal 15-30 46 49Tipperary Crystal 15-30 59 99 Cristal d'Arques 15-30 103  117 Waterford, Galway, Tipperary and Cristal d'Arques are trade marks.

Example 8

Adhesive formulations were prepared as follows:

A. n-Butyl cyanoacrylate monomer containing 30% w/w dibutyl phthalate.

B. Formulation A plus 0.2% methyltriacetoxy silane.

C. n-Butyl CA monomer control.

Formulation B was prepared by first dissolving the silane in theplasticizer and then adding this solution to the CA monomer to give thefinal adhesive formulation.

Soda glass test pieces of dimensions 50.8×25.4×4 mm were cleaned withisopropyl alcohol and deionized water and allowed to dry. Overlappedjoints with a bonded area of 322.5 mm² were prepared with each adhesiveand allowed to cure for 24 hours at RT (2° C.+3° C.). The boundaries ofthe joint were marked. One end of each bonded assembly was clamped to asupport. A weight (5 kg) was suspended from the other end of the jointto give a static stress of 0.16N/mm² The test rig was stored at 20°C.+3° C. and the bonds examined weekly for failure or any indication ofslippage or creep in the bonded overlap. After three months the bondinvolving the control adhesive (Formulation C above) was observed tohave failed or come apart. The bonds prepared with Formulations A and Bwere still intact after sixteen months with no indication of movement inthe bond line. At this stage the tests were discontinued. A formulationcontaining a relatively large percentage w/w plasticizer would normallybe expected to allow slippage or creep under the conditions of thisExample. Surprisingly no such effects were observed for Formulation Acontaining 33% w/w dibutlyphthalate.

Example 9

Cyanoacrylate based adhesive products or formulations as described belowwere used to prepare glass-glass bonds using the method outlined inExample 2. The bonds were cured for 24 hours at RT and then placed on aninternal window ledge with full exposure to daylight. The bonds wereexamined weekly for (a) bond failure and (b) yellowing or otherdiscoloration of the bond line. The attached results show that none ofthe bonds showed any change in appearance after thirteen months and bondfailure was only observed with bonds prepared with unplasticizedadhesives (Formulations A and B).

Formulations were as follows (DBP=dibutylphthalate, CA=cyanoacrylate).Formulations containing silanes were prepared as described in Example8.:

A. Ethyl CA adhesive (Loctite product no. 406 All Loctite products areavailable commercially from Loctite (Ireland) Limited, Dublin, Irelandor Loctite Corporation, Hartford Conn., USA).

B. n-Butyl CA monomer+0.5% Calixarene.

C. n-Butyl CA (Loctite 413)+20% DBP+0.5% Calixarene.

D. n-Butyl CA (Loctite 413)+30% DBP+0.5% Calixarene.

E. n-Butyl CA (Loctite 413)+20% DBP+0.2% vinyltriacetoxysilane+0.5%Calixarene.

F. n-Butyl CA (Loctite 413)+20% DBP+0.2% methyl triacetoxysilane+0.5%Calixarene.

G. n-Butyl CA Monomer+20% DBP.

H. n-Butyl CA Monomer+20% DBP+0.05% 3-(methacryloxy)propyltrimethoxysilane.

I. n-Butyl CA Monomer+20% DBP+0.05% 3-(methacryloxy)propyltrimethoxysilane.

J. n-Butyl CA Monomer+30% DBP.

K. n-Butyl CA Monomer+20% DBP+2.0% 3-(methacryloxy)propyltrimethoxysilane.

L. n-Butyl CA Monomer+20% DBP+1.0% vinyltriacetoxysilane.

M. n-Butyl CA Monomer+20% DBP+0.2% methyltriacetoxysilane.

Results (Example 9)

Durability and Resistance to Yellowing of Glass-Glass Bonds Exposed toDaylight for 18 months. The test was discontinued after 18 months.

ADHESIVE OBSERVATIONS after 18 Months A and B Debonded < 8 months Nodiscoloration. C, D, E, F, G, H, I, J, K, L and M No debonding oryellowing.

Example 10

Dibutyl phthalate was added to Loctite product number 413 (acommercially available n-butyl cyanoacrylate adhesive) at concentrationsof zero, 10, 15, 18, 21, 24 and 27% w/w. These adhesive mixtures wereeach divided into two parts; one part in each case being kept unchangedas comparative control while the second part was altered by the additionof 0.2% methyltriacetoxy silane.

The adhesives were then used to bond glass test pieces as described inExample 2. After curing at RT for 24 hours the bonds were tested fordurability using the dishwasher cleaning procedure described in Example2. The results are summarized below and show the following:

a) Standard butyl cyanoacrylate adhesives, as exemplified by Loctiteproduct number 413, do not give a durable bond on glass.

b) The addition of plasticizer alone, even at concentrations of up to27% w/w, give only a moderate improvement in glass bonding durability.

c) Adhesive formulations containing a combination of butylcyanoacrylate, plasticizer and silane show a moderate improvement indurability when used to bond glass but the most significant benefit isonly achieved if the plasticizer concentration exceeds a threshold levelof about 21 to 27%.

Formulation with Loctite Product Dishwasher Durability No. 413 (Cycles)DBP (%) Silane (%) Run 1 Run 2 Run 3 10 Zero 2 2 4 15 Zero 2 3 3 18 Zero3 4 4 21 Zero 3 4 5 24 Zero 4 4 5 27 Zero 5 6 6 10 0.2 5 6 7 15 0.2 7 78 18 0.2 7 7 7 21 0.2 7 7 60 24 0.2 7 7 60 27 0.2 116 116 116 ControlsZero Zero 2 3 4 Zero 0.2 5 7 8

Industrial Applicability

This invention provides adhesive compositions which are articles ofmanufacture.

What is claimed is:
 1. A one-part adhesive composition comprising: (a) acyanoacrylate monomer; (b) at least one plasticizer in the amount of 28to 60% w/w by weight of the composition; and (c) at least one silane inthe amount of 0.1 to % to 5.0% w/w by weight of the composition.
 2. Anadhesive composition according to claim 1 wherein the plasticizercontent is in the range of 28 to 40% w/w.
 3. An adhesive compositionaccording to claim 1 wherein the plasticizer content is in the range 28to 35% w/w.
 4. An adhesive composition according to claim 1 wherein thesilane content is in the range 0.02 to 3.0% w/w.
 5. An adhesivecomposition according to claim 1 wherein the silane content is in therange of 0.05 to 1.0% w/w.
 6. An adhesive composition according to claim1 wherein the plasticizer is selected from the group consisting of alkylphthalates, azelates, adipates, sebacates, citrates, phosphates,succinates, benzoates and trimellitates.
 7. An adhesive compositionaccording to claim 1 wherein the silane is selected from the silanes ofthe Formula: R′_((4−n)) Si(OR″)_(n) wherein: n=1 to 4; and each R′ andR″ which may be the same or different represents H, hydrocarbyl, aryl,hydrocarbylaryl or a substituted derivative thereof.
 8. An adhesivecomposition according to claim 7 wherein: n is 2 or
 3. 9. An adhesivecomposition according to claim 7 wherein: R″ is a member selected fromthe group consisting of C₁-C₅ alkyl, C₁-C₅ alkenyl, and —CO—R″′, whereinR″′ is a member selected from the group consisting of C₁-C₅ alkyl andC₁-C₅ alkenyl, or a substituted derivative thereof.
 10. An adhesivecomposition according to claim 7 wherein: R′ is a member selected fromthe group consisting of C₁-C₅ alkyl, C₁-C₅ alkenyl,

wherein m is 0 to 5 or —(CH₂)_(m)—O—CO—R″′ wherein R″′ is a memberselected from the group consisting of C₁-C₅ alkyl and C₁-C₅ alkenyl or asubstituted derivative thereof and m is 0 to
 5. 11. An adhesivecomposition according to any preceding claim wherein the silane isselected from the group consisting of vinyltriethoxy silane,vinyltrimethoxy silane, glicidoxypropyltrimethoxy silane, ethyltriethoxysilane, dimethyldiacetoxy silane, propyltriacetoxy silanevinylmethyldiacetoxy silane, methyltriacetoxy silane,3-(methacryloxy/propyltrimethoxy silane and vinyltriacetoxy silane. 12.An adhesive composition according to claim 1 wherein the silane isselected from the silanes of the general formula:

wherein R₁, R₂, R₃, and R₄, each independently represent hydrocarbyl,aryl, hydrocarbylaryl, or a substituted derivative thereof, H or halogenor the group —OR₅ wherein R₅ represents hydrocarbyl, aryl orhydrocarbylaryl or a substituted derivative thereof and any two of thegroups R₁, R₂, R₃ and R₄ may be taken together with the silicon atom toform a cycle; with the proviso that at least one of R₁, R₂, R₃ or R₄represents hydrocarbyl, aryl, hydrocarbylaryl or a substitutedderivative thereof.
 13. An adhesive composition according to claim 1wherein the monomer is butyl cyanoacrylate.
 14. An adhesive compositionaccording to claim 1 wherein the monomer is n-butyl cyanoacrylate.
 15. Amethod of bonding substrates which comprises the steps of applying aone-part adhesive composition according to claim 1 to at least one ofthe substrates and bringing the substrates together.
 16. The methodaccording to claim 15, wherein at least one of the substrates isconstructed of glass.
 17. An adhesive composition as in claim 1 whereinthe cyanoacrylate monomer is of the formula CH₂═C(CN)COOR where R isalkyl of 4-10 carbon atoms, or an alkoxyalkyl having 1-10 carbon atomsin the alkoxy group and 4-10 atoms in the alkyl group therein.
 18. Anadhesive as in claim 17 wherein the silane has the formula: R′_((4−n))Si(OR″)_(n) where n is 1-4; each R′ is the same or different and is H,or a unsubstituted or substituted hydrocarbyl, aryl or hydrocarbylarylgroup; and each R″ is the same or different and is H or a unsubstitutedor substituted group selected from C₁₋₅ akyl, C₁₋₅ slkenyl and —CO—R″′where R″′ is C₁₋₅ akyl or C₁₋₅ alkenyl.
 19. An adhesive as in claim 17wherein R is butyl or octyl.
 20. An article formed by bonding a pair ofsubstrates with an adhesive composition as in claim
 1. 21. An adhesivebond formed between two substrates, at least one of which is glass, thebond formed of a cured adhesive, the adhesive having a composition as inclaim
 1. 22. A one part adhesive comprising: (a) a cyanoacrylatemonomer; (b) at least one plasticizer in the amount of 28 to 60% w/w byweight of the composition; and (c) at least one silane in the amount of0.01% to 5.0% w/w by weight of the composition, wherein the silane isselected from the group consisting of vinyltriethoxy silane,vinyltrimethoxy silane, glycidoxypropyltrimethoxy silane, ethyltriethoxysilane, dimethyldiacetoxy silane, propyltriacetoxy silane,vinylmethyldiacetoxy silane, methyltriacetoxy silane,3-(methacryloxy)propyltrimethoxy silane, and vinyltriacetoxy silane. 23.An adhesive composition as in claim 22 wherein the plasticizer is in theamount of 28-40%.
 24. An adhesive composition as in claim 22 wherein theplasticizer is in the amount of 28-35%.
 25. A one-part adhesivecomposition comprising: (a) a cyanoacrylate monomer; (b) at least oneplasticizer in the amount of 25 to 60% w/w by weight of the composition;and (c) at least one silane in the amount of 0.1 to % to 5.0% w/w byweight of the composition, the silane having the formula: R′_((4−n))Si(OR″)_(n)  where n is 1-4; each R′ is the same or different and is H,or a unsubstituted or substituted hydrocarbyl, aryl, or hydrocarbylarylgroup; and each R″ is the same or different and is H or a unsubstitutedor substituted group selected from C₁₋₅ alkyl, C₁₋₅ alkenyl and —CO—R″′where R″′ is C₁₋₅ alkyl, or C₁₋₅ alkenyl.
 26. A method of bonding a pairof substrates, at least one of which is glass, the method comprisingapplying a composition as in claim 25 to at least one of the substratesand bringing the substrates together.
 27. A method as in claim 26 wherethe pair of substrates, when bonded, forms a article of dish ware. 28.An article formed by bonding a pair of substrates according to themethod of claim
 26. 29. A method of repairing a broken articlecomprising at least first and second broken pieces having mutual matingsurfaces, the method comprising applying an adhesive composition as inclaim 25 to at least one said mutual mating surface, and joining thefirst and second broken piece along said mating surfaces.
 30. A methodas in claim 29 wherein the mating surfaces of the broken article areglass surfaces.
 31. A method as in claim 29 wherein the plasticizer ispresent in the adhesive composition in an amount of at least 28% byweight of the composition.
 32. An article formed by bonding a pair ofsubstrates with an adhesive composition as in claim
 25. 33. An adhesivebond formed between two substrates, at least one of which is glass,wherein the bond is formed of a cured adhesive, the adhesive having acomposition as in claim 25.